The applicant, a dentist currently in a pediatric dentistry residency and starting a Ph.D. program has proposed a plan of study that will allow her to receive advanced training in basic science, while completing her residency. The planned curriculum is one that will lead to a Ph.D. in the Department of Oral and Craniofacial Biological Sciences of the Univ. of Maryland Dental School, with a special emphasis in neuroscience. The research question to be addressed will require the applicant to become proficient in the field of pain, both in terms of its measurement in people and its biological mechanisms. The applicant's long term plan is to combine a research, educational, and clinical practice career. Epidemiological, clinical, and laboratory studies suggest that, in general, women are more sensitive to pain than men. Many experimental studies using controlled noxious stimuli in laboratory settings report that females show greater sensitivity to painful stimuli than men do. However, a sizable number of studies report no significant gender difference. A reasonable interpretation of these disparate results is that gender differences in pain sensitivity do exist, but not in all circumstances. Other studies indicate that pain sensitivity fluctuates with changes in levels of certain endogenous substances, and this fluctuation is greater in females than in males. One component of this fluctuation in women would be the menstrual cycle, which dramatically modulates the levels of several substances, particularly gonadal hormones. This project proposes evaluating pain perception in a large group of young female subjects repeatedly over several weeks, and simultaneously determining the plasma concentrations of estrogen and progesterone. Then, correlations will be sought with respect to variations in pain sensitivity, and variations in systemic concentrations of the aforementioned substances. Comparable psychophysical and serum testosterone measures will also be made on an age-matched group of men. The specific hypotheses to be evaluated are as follows: 1) the fluctuations in some pain measures will be significantly larger for female than for male subjects; 2) for those times and pain measures that do show gender differences, we expect the differences to be more prominent in the head and neck region than elsewhere on the body; 3) for women, some pain measures (but not necessarily all) will be significantly correlated with circulating levels of estrogen and progesterone; 4) for men, some pain measures will be significantly correlated with circulating levels of testosterone; 5) under conditions that evoke an endogenous antinociceptive system, the degree of the induced hypalgesia will be inversely proportional to circulating levels of estrogen (women) or testosterone (men).